Classifications

• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06M—TREATMENT, NOT PROVIDED FOR ELSEWHERE IN CLASS D06, OF FIBRES, THREADS, YARNS, FABRICS, FEATHERS OR FIBROUS GOODS MADE FROM SUCH MATERIALS
  • D06M13/00—Treating fibres, threads, yarns, fabrics or fibrous goods made from such materials, with non-macromolecular organic compounds; Such treatment combined with mechanical treatment
  • D06M13/08—Treating fibres, threads, yarns, fabrics or fibrous goods made from such materials, with non-macromolecular organic compounds; Such treatment combined with mechanical treatment with halogenated hydrocarbons
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
  • C04B41/009—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone characterised by the material treated
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
  • C04B41/53—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone involving the removal of at least part of the materials of the treated article, e.g. etching, drying of hardened concrete
  • C04B41/5338—Etching
  • C04B41/5353—Wet etching, e.g. with etchants dissolved in organic solvents

Definitions

• the present invention relates to the treatment of ceramic fibers, and, more especially, to the treatment of ceramic fibers based on silicon nitride, silicon carbide or silicon carbonitride to enhance the surface properties thereof.
• polystyrene resins are well known products which may be in the form of monomers, oligomers, cyclic or linear polymers, and also resinous polymers; they may be prepared by a wide variety of processes utilizing a wide range of starting materials.
• these polymers (optionally after melting, if originally they are in the solid state) are processed into continuous filaments by any known means, in particular by extrusion through dies, and are then pyrolyzed (after an optional crosslinking to increase their high temperature strength) to yield the desired ceramic fiber final products.
• the ceramic fibers based on SiC and/or Si 3 N 4 produced by this method may in certain instances have insufficient surface qualities. This may translate into an appreciable change in the overall performance of the fibers.
• surface quality is particularly intended the potential presence, on the one hand, of different chemical impurities, such as, for example, silica, and, on the other, of critical defects, which adversely affect the overall performance of the fibers in respect of certain mechanical properties, such as, for example, rupture or breaking strength.
• a major object of the present invention is the provision of a treatment for substantially improving the surface and/or mechanical properties of ceramic fibers based on silicon carbide, silicon nitride or silicon carbonitride.
• the present invention features contacting such ceramic fibers with hydrofluoric acid, HF.
• the ceramic fiber subjected to the treatment according to the invention is typically a fiber based on silicon carbide, silicon nitride or silicon carbonitride. It has nevertheless also been found that the treatment according to the invention is more generically applicable to any ceramic fibers of a third category, namely, those based on silicon, carbon and nitrogen.
• These fibers may be single filament, or multifilament, i.e., they may comprise a plurality of monofilaments, whether or not intertwined.
• the fibers based on SiC and/or Si 3 N 4 treated according to the invention are preferably produced from the aforesaid organometallic polymer precursors, but it will be appreciated that the treatment of fibers produced by any other means is also within the scope of this invention.
• organometallic polymer precursors suitable for the preparation of the starting material ceramic fibers are the polysilanes, polycarbosilanes, polycarbodisilanes, polysilazanes and poly(disilyl)silazanes.
• the organometallic polymers belonging to the first three categories of precursors are particularly suitable for the preparation of SiC fibers.
• organometallic polymers of the polysilazane and poly(disilyl)silazane type are more particularly suitable for the preparation of Si 3 N 4 or mixed Si 3 N 4 /SiC fibers.
• the desired ceramic fiber After the desired ceramic fiber has been produced in the above manner, it is next contacted with hydrofluoric acid, HF.
• hydrofluoric acid is preferably employed in the form of a liquid solution, but the use of gaseous hydrofluoric acid is also within the scope of the invention.
• liquid solution is preferably an aqueous solution.
• the proportion of the dilution, or concentration of the HF acid in said solution advantageously ranges from 3% to 30% by volume and preferably is around 10% by volume.
• the duration of the treatment may vary over wide limits, i.e., within a period of time ranging from several minutes to several hours, preferably from 5 min. to 5 hours. However, treatment periods ranging from 5 to 60 min are generally sufficient to obtain the desired result.
• the temperature at which the treatment is carried out may range from ambient temperature to 100.C. Preferably, it ranges from 20° to 30° C. and even more preferably is around 25° C.
• the three interdependent parameters i.e., concentration, time and temperature
• concentration, time and temperature are regulated in consideration of the fact that an overly strong or lengthy treatment (excessive HF concentration and/or temperature too high), may damage the fiber by modifying its core properties (reduction in density, appearance of pitting corrosion, modification of morphology, etc.).
• the treatment according to the invention is discontinued when a perfectly smooth and clean surface is observed.
• the fibers treated according to the invention have important applications as reinforcing materials in composites having a glass, metal or ceramic matrix. It is known to this art that the properties of the fiber/matrix interface in such materials are highly important.
• a polymer of the polysilazane type was initially prepared by rigorously following the procedure described in Example 18 of FR-A-2,577,933 assigned to the assignee hereof, i.e., by polymerizing, in the presence of triflic acid, a coammonolysate obtained by the ammonolysis in a solvent medium of a mixture of methyltrichlorosilane and dimethyldichlorosilane in a molar ratio of 67/33.
• the resulting polysilazane was then melted, extruded in the form of fibers and then rendered infusible.
• the fibers were then pyrolyzed under an inert atmosphere (nitrogen or argon) at a temperature of from 1,000° to 1500° C.
• an inert atmosphere nitrogen or argon
• the properties of the fibers obtained were the following:
• Ra 0.8 ⁇ m (mean size of critical defect)
• This fiber had a surface layer of silica, SiO 2 , characterized by ESCA.
• the Ra was measured by scanning electron microscope examination of rupture faces
• m is a parameter indicative of the stress distribution at rupture of a material; the greater the dispersion, the smaller is m.
• This fiber was then treated at 25° C. and for 30 min with a 10% by volume aqueous solution of hydrofluoric acid.
• the properties of the fiber were the following:

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Ceramic Engineering (AREA)
• Materials Engineering (AREA)
• Structural Engineering (AREA)
• Organic Chemistry (AREA)
• Textile Engineering (AREA)
• Inorganic Fibers (AREA)
• Chemical Or Physical Treatment Of Fibers (AREA)
• Chemical Treatment Of Fibers During Manufacturing Processes (AREA)
• Treatments For Attaching Organic Compounds To Fibrous Goods (AREA)
• Silicon Compounds (AREA)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

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Cited By (4)

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Citations (2)

Family Cites Families (8)

• 1988
  • 1988-05-10 FR FR8806270A patent/FR2631334A1/fr not_active Withdrawn
• 1989
  • 1989-04-28 EP EP89401217A patent/EP0342092A1/fr not_active Ceased
  • 1989-05-08 BR BR898902139A patent/BR8902139A/pt unknown
  • 1989-05-08 NO NO89891875A patent/NO891875L/no unknown
  • 1989-05-08 IL IL90227A patent/IL90227A0/xx unknown
  • 1989-05-09 PT PT90502A patent/PT90502A/pt not_active Application Discontinuation
  • 1989-05-09 CN CN89104286A patent/CN1038265A/zh active Pending
  • 1989-05-09 DK DK226289A patent/DK226289A/da not_active Application Discontinuation
  • 1989-05-09 KR KR1019890006197A patent/KR890017418A/ko not_active Application Discontinuation
  • 1989-05-09 AU AU34585/89A patent/AU617465B2/en not_active Ceased
  • 1989-05-09 FI FI892233A patent/FI892233A/fi not_active IP Right Cessation
  • 1989-05-09 ZA ZA893415A patent/ZA893415B/xx unknown
  • 1989-05-10 JP JP1115235A patent/JPH0253964A/ja active Granted
  • 1989-05-10 US US07/349,823 patent/US5043045A/en not_active Expired - Fee Related

Patent Citations (2)

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